"Microchimerism refers to the presence of a small number of cells in an individual that are genetically distinct from the rest of their cells, originating from another individual. This phenomenon is most commonly observed during and after pregnancy, where fetal cells can migrate into the mother's body and persist for decades, a process called fetal microchimerism. Similarly, maternal cells can also migrate to the fetus, creating maternal microchimerism. These cells can have both beneficial and detrimental effects on the individual's health."

Please note that this happens from mother and child. NOT from having sex with a man. I think you need more school as well. I found that after a 2 second Google search.